Fluororesin films, laminate produced by using the same, and process for producing laminate

ABSTRACT

A tetrafluoroethylene-ethylene copolymer (ETFE) film, wherein polar groups are present on the surface of the film after a surface treatment, and the surface roughness R a  is at most the surface roughness R a  of the surface of an untreated film; an ETFE film, wherein polar groups are present on the surface of the film after a surface treatment, and the amount of a weak boundary layer is at most one time of the amount of a weak boundary layer on the surface of an untreated film; a laminate employing such a film having an extremely excellent bonding strength; and a process for producing it with a mass production property.

TECHNICAL FIELD

The present invention relates to a tetrafluoroethylene-ethylenecopolymer (hereinafter referred to as ETFE) film, a laminate employingit and a process for producing the laminate.

BACKGROUND ART

Fluororesins such as ETFE are excellent in chemical resistance and stainresistance. A laminate obtained by laminating a fluororesin film on asubstrate such as a metal or a plastic, is used in a wide range offields including, for example, a floor covering, a copy board, a wallpaper, a roof covering, a top plate for gas cooking tables, a gas rangehood fan, a surface protecting film and a cover for solar cells.However, to bond a fluororesin film such as an ETFE film on a substrateby an adhesive, a surface treatment which imparts physical and chemicalimprovements to the surface of the fluororesin is required. This is toimprove wettability of the adhesive to the fluororesin having a lowsurface energy.

As the surface treatment method, a corona discharge treatment hascommonly been known. Further, as a method in place of the coronadischarge treatment, to improve the bonding property, a process of RFsputtering under conditions of high vacuum and high electric powerdensity (JP-A-51-125455), a process of RF sputtering in a specialatmosphere gas (JP-A-6-285988) and a process of RF sputtering for a longperiod of time (JP-A-6-298971) have been proposed. However, none of ETFEfilms subjected to the surface treatment by the above-mentioned methodshave not had a practically adequate bonding strength.

The object of the present invention is to provide an ETFE film whichprovides an excellent bonding strength, a laminate employing said ETFEfilm and a process for producing the laminate.

DISCLOSURE OF THE INVENTION

The present invention provides a surface-treatedtetrafluoroethylene-ethylene copolymer film, wherein polar groups arepresent on the surface of the above-mentioned surface-treated film, andthe surface roughness R_(a) of the surface of the surface-treated filmis at most the surface roughness R_(a) of the surface of an untreatedtetrafluoroethylene-ethylene copolymer film.

The present invention further provides a surface-treatedtetrafluoroethylene-ethylene copolymer (ETFE) film, wherein polar groupsare present on the surface of the above-mentioned surface-treated film,and the amount of fluorine atoms present on the surface of an aluminumthin plate obtained by hot-pressing the aluminum thin plate on thesurface of the above-mentioned surface-treated film at 100° C. under asurface pressure of 21 kgf/cm² for 10 minutes, followed by cooling toroom temperature and separation, is at most one time of the amount offluorine atoms present on the surface of an aluminum thin plate obtainedby the above-mentioned hot-pressing of the above-mentioned aluminum thinplate on the surface of a surface-untreated tetrafluoroethylene-ethylenecopolymer film, followed by cooling to room temperature and separation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a figure illustrating the relation between the adhesionstrength between an ETFE film and an ethylene-vinyl acetate copolymer(EVA) film, and the amount of fluorine transferred.

FIG. 2 is a figure illustrating the relation between the bondingstrength between an ETFE film and a soft vinyl chloride film(hereinafter referred to simply as vinyl chloride), and the amount offluorine transferred.

FIG. 3 is a schematic cross-sectional view explaining one example of anRF bombard apparatus to be used for the surface treatment of an ETFEfilm in the present invention.

FIG. 4 is a schematic cross-sectional view explaining one example of aDC bombard apparatus to be used for the surface treatment of an ETFEfilm in the present invention.

FIG. 5 is a figure illustrating ESCA spectra on the surface of asurface-treated ETFE film of the present invention.

FIG. 6 is a figure illustrating ESCA spectra on the surface of an ETFEfilm which is subjected to a corona discharge treatment.

FIG. 7 is a schematic oblique view explaining an apparatus and a processfor producing a laminate of an ETFE film with vinyl chloride.

FIG. 8 is a schematic oblique view explaining an apparatus and a processfor producing a laminate of an ETFE film with a stainless steel plate(hereinafter referred to simply as SUS plate).

BEST MODE FOR CARRYING OUT THE INVENTION

The present inventors have conducted extensive studies on the relationbetween the bonding strength and the condition of the surface of thesurface-treated ETFE film, and as a result, they have found that asurface-treated ETFE film wherein polar groups are present on thesurface of the surface-treated film, and the amount of a weak boundarylayer bonded on the surface of the film by a weak bonding strength issmall, provides an extremely good bonding strength. The weak boundarylayer is composed mainly of oligomers formed by breakage of a polymer.On the surface of a fluororesin film such as an ETFE film, a weakboundary layer (hereinafter referred to as WBL) is present, and thepresence of WBL will be a significant impact on a bonding property or anadhesion property. It has been found that such WBL merely bonds with thefilm substrate by a weak force, and impairs the bonding property or theadhesion property, and it is necessary that the amount of WBL is smallfor an excellent bonding strength and adhesion strength. Further, it hasbeen found that it is necessary not to increase, preferably to reduce,the amount of WBL present on the surface of the ETFE film before thesurface treatment, by the surface treatment, to obtain an excellentbonding strength and adhesion strength.

The present inventors have conducted extensive studies on the relationbetween the bonding strength and functional groups of thesurface-treated ETFE film, and as a result, they have found itpreferable that hydroxyl groups and/or carbonyl groups are present, asthe polar groups, to impart the bonding property. By the surfacetreatment of the present invention, an ETFE film wherein hydroxyl groupsand carbonyl groups are present on the surface, can easily be obtained.

The surface functional groups on the surface-treated ETFE film can beidentified by ESCA (Electron Spectroscopy for Chemical Analysis) methodor by a chemical modification method.

Further, as a result of extensive studies on the relation between thebonding strength and the surface roughness of the surface-treated ETFEfilm, it has been found that an ETFE film wherein the surface roughnessof the surface of the surface-treated film is about equal to or lessthan the surface roughness of the surface of an untreated ETFE film,provides an extremely excellent bonding strength. The surface of thesurface-treated ETFE film is preferably under a condition free fromsignificant irregularities (a condition under which corn-likeprojections are not formed). It is particularly preferred that acrystalline structure under the surface-untreated state is not impairedafter the surface treatment.

The surface roughness in the present invention is represented by thearithmetical mean surface roughness R^(a) (hereinafter referred tosimply as R_(a)) as defined by JIS B0601.

In the present invention, R_(a) was measured by using AFM (Atomic ForceMicroscope) at non-contact movement dynamic mode. R_(a) of the ETFE filmof the present invention was measured by using AFM. As a result, R_(a)was equal to or less than the untreated ETFE film. Further, the ETFEfilm having such R_(a) of the present invention had an excellent bondingstrength and adhesion strength. It has been found that particularly whenR_(a) is at most 10 nm, an excellent bonding strength and adhesionstrength can be obtained.

The present invention further provides a laminate which comprises asubstrate and the above-mentioned surface-treatment ETFE film laminatedon the substrate so that the surface of the surface-treated film facesthe substrate. It is particularly preferred that the laminate furtherhas an adhesive for lamination (hereinafter referred to simply asadhesive) between the above-mentioned substrate and the above-mentionedtetrafluoroethylene-ethylene copolymer film, and the above-mentionedsubstrate and the above-mentioned tetrafluoroethylene-ethylene copolymerfilm are bonded each other by the above-mentioned adhesive.

By any of the conventional corona discharge treatment, or the abovesurface treatment method such as a process of RF sputtering underconditions of high vacuum and a high electrical power density(JP-A-51-125455), a process of RF sputtering in a special atmosphere gas(JP-A-6-285988) or a process of RF sputtering for a long period of time(JP-A-6-298971), polar groups can be introduced by the surfacetreatment. However, by the surface treatment, WBL with an amount ofexceeding the amount of WBL on the untreated surface, will form, and thesurface having R_(a) of at least the surface of the untreated film, willbe formed.

On the other hand, the present inventors have found that an ETFE filmhaving WBL and R_(a) in an amount of equal to or less than the untreatedETFE film can be obtained by conducting the surface treatment of theETFE film by the following method, and the treated ETFE film has anexcellent adhesion strength.

Among such surface treatment methods of an ETFE film, preferred is an RFbombard treatment. When radio frequency (RF) voltage is applied betweenelectrodes facing each other under reduced pressure for RF discharge,plasma of diluted air will form in the space between the electrodes. Theplasma contains active species such as radical atoms and ions. Theycollide against the substrate provided on the electrode or provided inthe plasma, and may change the condition of the surface of the substratephysically and chemically. RF bombard treatment is a method of utilizingthe effect and applying it to an improvement in the condition of thesurface. The bombard treatment is a treatment, which is characterized bya weak etching effect due to a mild sputtering, together with an effectof chemically improving the surface by the plasma. The treatmentcondition varies depending upon e.g. the type of the gas, the gaspressure, the introducing electric power, the distance between theelectrodes, and the part at which the substrate is provided.

Further, as the surface treatment method of an ETFE film, a DC (directcurrent) bombard method is also preferably employed. This is a treatmentwherein DC is employed instead of RF in the RF bombard method, andsimilar effects can be obtained. In the DC bombard treatment, directcurrent voltage is applied between electrodes facing each other to formplasma, and the surface is physically and chemically changed byutilizing the plasma. In the DC bombard treatment, the apparatus issimple as compared with the RF bombard treatment, whereby the DC bombardtreatment is likely to be carried out in a large scale, and it issuitable for mass production. However, a little contrivance is requiredfor apparatus conditions.

According to the RF bombard treatment or the DC bombard treatment, acontinuous treatment of roll to roll system can be carried out, wherebythe mass production property can be increased.

In the above-mentioned RF bombard treatment and DC bombard treatment,the introducing electric power is preferably an electric power densityof from 0.01 to 0.5 W/cm². The treatment time is preferably from 5 to300 seconds, more preferably from 5 to 60 seconds. These conditions arevery weak as compared with the RF sputtering process which has alreadybeen reported. However, they are enough for the formation of functionalgroups on the surface. On the contrary, if the introducing electricpower is too strong or the treatment time is too long, damages which areunfavorable for improving the adhesion property may be imparted to thefilm, such that the surface is excessively impaired, a large amount ofWBL will be formed, or the change in the composition may be caused.

The gas to be used in the above-mentioned RF bombard treatment and DCbombard treatment, is not particularly limited so long as it maygenerate plasma, and it makes polar groups be present on the surfaceafter the surface treatment. To improve wettability of the adhesive tothe ETFE film, and to remove WBL, a treatment by a gas containing aninert gas such as He gas, Ne gas, Ar gas, Kr gas or Xe gas, ispreferred. A treatment by a gas containing Ar gas is preferred in viewof economy, handling efficiency and desired results. Further, by atreatment by a gas containing an oxygen-containing compound such asoxygen, carbon dioxide, carbon monoxide, ozone, water vapor, nitrousoxide or acetone, oxygen-containing functional groups may be imparted tothe film, and WBL may be removed, during the bombard treatment, wherebythe bonding strength will improve. Further, with a purpose of formingnitrogen-containing functional groups, by a treatment by a gascontaining a nitrogen-containing compound such as nitrogen, nitrogendioxide, nitrogen monoxide or ammonia, polar groups may be formed, andWBL may be removed.

By conducting the RF bombard treatment or the DC bombard treatment underthe above-mentioned mild conditions, an ETFE film having the surfaceshape of the surface of a surface-untreated film maintained, havingR_(a) of equal to or less than the untreated ETFE film, having polargroups on the treated surface, and having an extremely small amount ofWBL, can be obtained. The ETFE film thus surface-treated, provides anextremely excellent bonding strength and adhesion strength.

By combining with an adhesive, a laminate having a very high bondingproperty which is practically adequate, and a surface which is excellentin water-vapor resistance, can be obtained. Further, a laminate havingan adequate adhesion strength with a film having a large amount of polargroups such as EVA, can be obtained without using an adhesive.

The improvement in the bonding strength or the adhesion strength isconsidered to be attributable to the fact that C—H bonds, C—F bonds orC—C bonds on the surface of ETFE are cut by the surface treatment, andthey react with e.g. water or oxygen when they are exposed in the air toform polar groups such as hydroxyl groups or carbonyl groups, and theyremove WBL present on the surface without generating irregularities onthe surface or newly forming WBL on the surface, as the condition ismild under reduced pressure. Further, it is considered that in the caseof treatment by a reactive gas such as oxygen, in addition to theabove-mentioned mechanism, active species in the plasma will react,whereby polar groups will be introduced on the treated surface.

Further, since the amount of WBL significantly influences the bondingproperty and the adhesion property as mentioned above, the presentinventors have considered that the amount of WBL may be applied to anevaluation of the bonding property or the adhesion property of thesurface-treated ETFE film, and devised a method for analyze the amountof fluorine transferred to an aluminum thin plate, as a method forquantitatively evaluate the amount of WBL.

Now, the amount of fluorine transferred will be explained. When afluororesin film such as an ETFE film is hot-pressed with a substrate,WBL present on the surface of the film will easily be transferred on thesubstrate. The amount transferred varies depending upon the pressingtemperature, the surface pressure or the type of the substrate to behot-pressed. To analyze the amount of WBL in the ETFE film, it issuitable to use an aluminum thin plate as a substrate, and to pressunder condition of a surface pressure of 21 kgf/cm² and a pressingtemperature of 100° C. The amount of WBL can be evaluated by the totalamount of fluorine atoms attached on the surface of the aluminum thinplate. The amount of fluorine transferred is defined as the ratio of theamount of fluorine atoms to the amount of aluminum atoms (atomic weightof fluorine [atomic %]/atomic weight of aluminum [atomic %]) based onthe analyzed value of composition on the surface of the aluminum thinplate by ESCA measurement.

In the present invention, the amount of fluorine atoms present on thesurface of an aluminum thin plate obtained by hot-pressing the aluminumthin plate on the surface of the surface-treated ETFE film at 100° C.under a surface pressure of 21 kgf/cm² for 10 minutes, followed bycooling to room temperature and separation, is preferably at most onetime of the amount of fluorine atoms present on the surface of analuminum thin plate obtained by the above-mentioned hot-pressing of theabove-mentioned aluminum thin plate on the surface of asurface-untreated ETFE film, followed by cooling to room temperature andseparation.

Here, the amount of fluorine atoms present on the surface of aluminumafter the separation, is the total amount of fluorine atoms contained inall molecules, high polymer molecules and compounds which containfluorine, present on the surface of aluminum after separated from theETFE film.

The surface roughness R_(a) on the surface of the surface-treated filmis also preferably at most the surface roughness R_(a) of the surface ofan untreated ETFE film.

The present inventors have further conducted extensive studies on therelation between the bonding strength or the adhesion strength of thesurface-treated ETFE film, and the amount of fluorine atoms transferredon the surface of an aluminum thin plate, which was in contact with thefilm, by hot-pressing the aluminum thin plate on the treated surface ofthe surface-treated ETFE film under a surface pressure of 21 kgf/cm² at100° C. for 10 minutes.

The relation between the adhesion strength between an ETFE film and anEVA film, and the amount of fluorine transferred on the surface of analuminum thin plate, which was in contact with the ETFE film, byhot-pressing the aluminum thin plate on the treated surface of thesurface-treated ETFE film under a surface pressure of 21 kgf/cm² at 100°C. for 10 minutes, is shown in FIG. 1.

As shown in FIG. 1, to obtain an adequate adhesion strength of an ETFEfilm having polar groups such as hydroxyl groups or carbonyl groups onthe surface of the film, the amount of fluorine transferred ispreferably about equal to or less than the untreated film. Namely, theadhesion strength between an ETFE film and an EVA film is controlled,not by the amount of functional groups, but by the amount of fluorinetransferred, and the smaller the amount of fluorine transferred, thehigher the adhesion strength, whereby the amount of fluorine transferredis preferably small.

The amount of fluorine transferred of an untreated film is about 0.2.Accordingly, the ETFE film of the present invention preferably has anamount of fluorine transferred of at most 0.2. A surface-treated ETFEfilm having an amount of fluorine transferred of at most 0.1, has aparticularly excellent bonding strength and adhesion strength.

The relation between the bonding strength of a laminate obtained bylamination with vinyl chloride by using an adhesive (an adhesivecontaining a thermoplastic polyester resin component as the maincomponent is used in this example) after boiling for 5 hours, and theamount of fluorine transferred, is shown in FIG. 2. As shown in FIG. 2,to obtain an ETFE film having oxygen-containing functional groups on thesurface of the film, and having an adequate bonding strength with vinylchloride (particularly a bonding strength maintained under conditions ofhigh temperature and high humidity), the amount of fluorine transferredis also preferably small, the amount of fluorine transferred isparticularly preferably about equal to or less than the untreated film,i.e. the amount of fluorine transferred is at most 0.2. Particularly, asurface-treated ETFE film having an amount of fluorine transferred of atmost 0.1 has a very excellent bonding strength and adhesion strength.

The examples in FIG. 1 and FIG. 2 are examples of surface treatment byAr gas. However, with respect to the relation between the bondingstrength and the adhesion strength, and the amount of fluorinetransferred, similar results can be obtained in a treatment by a gascontaining another inert gas, oxygen gas, carbon dioxide gas or nitrogengas, etc.

On the other hand, the amount of fluorine transferred of a film having acorona discharge treatment in the air applied thereto, is as large as0.98, and a surface-treated film having a lower amount of fluorinetransferred than the untreated film, can not be obtained. As largeamount of WBL is present, even when hydrophilic groups (such as hydroxylgroups and carbonyl groups) are introduced by the surface treatment, andthe wettability is improved, a durable bonding strength can not beobtained, and an adequate adhesion strength can not be obtained either.It is considered that by a conventional corona discharge surfacetreatment method in the air, the amount of WBL increases resulting fromthe surface treatment.

On the contrary, by the above-mentioned RF bombard treatment or DCbombard treatment under mild conditions under reduce pressure, asurface-treated ETFE film having an amount of fluorine transferred of atmost 0.1 can be obtained, and a high bonding strength and an excellentadhesion strength can be obtained. This is considered to be attributableto the fact that the very mild RF or DC bombard treatment under reducedpressure functions to wash WBL on the surface.

Further, according to the present invention, a surface-treated ETFEfilm, wherein hydroxyl groups and carbonyl groups are present on thesurface of the above-mentioned surface-treated film, and the surfaceroughness is at most 10 nm, can be provided.

The ETFE film of the present invention can easily be laminated with aso-called plastic sheet or film such as polyethylene, polypropylene,ABS, polystyrene, polyvinyl chloride, PET or acryl, by using anadhesive.

As the adhesive, a synthetic resin type adhesive represented by an epoxytype adhesive, a silicone type adhesive, a polyurethane type adhesive, aurea type adhesive, a melamine type adhesive, a phenol resin typeadhesive, a vinyl acetate type adhesive or a cyanoacrylate typeadhesive, may be mentioned. Further, an emulsion type adhesiverepresented by a vinyl acetate type resin dispersed in e.g. water, a hotmelt adhesive represented by an ethylene-vinyl acetate type or apolyamide type, or a synthetic rubber type adhesive represented bychloroprene rubber, may be mentioned. Further, an acryl type adhesive ora silicone type adhesive may be mentioned.

Further, by using the above-mentioned adhesive, the ETFE film can easilybe laminated with a metal such as aluminum, a SUS plate, galvaniumsteel, galvanized steel or iron.

Further, by using the above-mentioned adhesive, the ETFE film can belaminated with a fluororesin such as ETFE or PFA(tetrafluoroethylene-perfluoro(alkoxyethylene) copolymer).

Among the above-mentioned adhesives, particularly effective is anadhesive containing a thermoplastic polyester resin component(hereinafter referred to as polyester type adhesive).

The thermoplastic polyester resin is one obtainable bydehydration-condensation reaction of a dibasic acid with a diol. Thedibasic acid may, for example, be an aliphatic dibasic acid such asadipic acid, azelaic acid, sebacic acid, succinic acid or suberic acid,or an aromatic dibasic acid such as isophthalic acid, terephthalic acid,orthophthalic acid or naphthalene dicarboxylic acid. The diol may, forexample, be ethylene glycol, diethylene glycol, 1,4-butanediol,1,6-hexanediol or neopentyl glycol.

The above-mentioned thermoplastic polyester resin is synthesized by adehydration-condensation reaction at a temperature of preferably about240° C.

An additive may be used together with the thermoplastic polyester resinto improve properties as an adhesive. The additive may, for example, bea flow control agent such as benzoin or dimethylterephthalate.

Further, an isocyanate group-containing compound as a curing agent maybe used together therewith to improve the bonding strength.

Further, to improve the bonding strength with fibrous substrate such asfabric, the polyester resin may undergo a urethane modification toincrease the adhesion property.

Further, to bond the polyester type adhesive with both thesurface-treated fluororesin and a metal, the polyester resin may undergoan epoxy modification.

The epoxy modification is carried out by carrying out the terminal epoxymodification (preferably by adding a predetermined amount of an epoxyresin such as bisphenol A type to the polyester resin followed byreaction at about 180° C.) after the polyester resin is synthesized. Theepoxy modification is effective to improve the bonding strength to ametal, and extremely effective to improve boiling water resistance andchemical resistance.

The epoxy modification is carried out by adding an epoxy resin with asuitable amount to modify the terminal carboxyl groups of thepreliminarily synthesized polyester resin to epoxy.

The preferred amount of the epoxy resin to be added varies dependingupon the type of the substrate to be bonded to the above-mentioned ETFEfilm. For example, when the ETFE film is bonded to a metal, the epoxyresin may be added with an amount required to completely modify theterminal carboxyl groups of the polyester resin, or the epoxy resin withan excess amount may be added so that free epoxy resin which is notinvolved in the modification is present to such an extent that heat flowof the epoxy modified polyester resin is not prevented when the adhesiveis heated. On the other hand, when the ETFE film is bonded to vinylchloride, the degree of modification due to the epoxy resin may beslight, or there may be no modification (namely, the amount of the epoxyresin to be added to the polyester resin may be small or none). This isattributable to the fact that the epoxy resin swells by a plasticizercontained in vinyl chloride, whereby the cohesion strength tends to below.

As the epoxy resin to be used for the epoxy modification, theabove-mentioned bisphenol A type resin having a bisphenol skeleton, ahydrogenated bisphenol A type resin, a diol type resin having abisphenol skeleton changed to a flexible methylene chain, a glycol typeresin having a bisphenol skeleton changed to an ether chain, may, forexample, be mentioned. By changing the skeleton structure of such anepoxy resin, the glass transition point of the adhesive when cured canoptionally be changed.

An epoxy resin of bisphenol A type having an epoxy equivalent of at alevel of from 500 to 1000, is particularly effective.

Further, a curing agent may be used together with the epoxy-modifiedpolyester type adhesive or the urethane-modified polyester typeadhesive. As the curing agent, a polyisocyanate having at least twoisocyanate groups per molecule is preferably used. It may, for example,be an aromatic polyisocyanate such as tolylene diisocyanate,4,4′-diphenylmethane diisocyanate or xylylene diisocyanate, an alicyclicpolyisocyanate such as isophorone diisocyanate, or an aliphaticpolyisocyanate such as hexamethylene diisocyanate. Further, an additionproduct, a biuret product or an isocyanurate product of theabove-mentioned polyisocyanate with trimethylol propane may, forexample, be mentioned. For a two pack type wherein a curing agent isused together, there is a pot life, and it is more preferred to use aso-called block isocyanate which dissociate at a high temperature tofunction as a curing agent.

Here, the method for producing the above-mentioned various thermoplasticpolyester resins is not particularly limited to Examples as describedhereinafter.

The thickness of the adhesive coated is preferably at least 3 μm as acoating thickness after dried. When an ETFE film having a thickness ofless than 500 μm is laminated, it is suitably from 5 to 10 μm. Further,when a thick ETFE film having a thickness of at least 500 μm is bonded,the thickness of about 20 μm is preferred.

The method for lamination is not particularly limited. However,so-called dry laminate is suitable wherein a solvent is evaporated afterthe adhesive is coated on the film, followed by lamination. By makingthe films pass between nip rolls maintained to a temperature of at leasta temperature at which the solvent is dried during the lamination, thebonding strength will further increase.

An additive such as a pigment, a leveling agent, a defoaming agent or anultraviolet absorber, may be added to such an adhesive.

The present invention provides a process for producing a laminate, whichcomprises laminating an ETFE film having RF bombard treatment or DCbombard treatment applied to its surface, and another substrate, by adry lamination method.

The present invention further provides a process for producing alaminate, which comprises coating an adhesive for lamination on an ETFEfilm having RF bombard treatment or DC bombard treatment applied to itssurface, followed by drying the above-mentioned adhesive, and bondinganother substrate with the above-mentioned surface-treatedtetrafluoroethylene-ethylene copolymer film by the above-mentionedadhesive, for lamination by a dry lamination method.

Both sides of the ETFE film may be treated by the RF bombard treatmentor the DC bombard treatment. In such a case, the adhesive may be coatedonly on the side to be bonded to another substrate.

The above-mentioned adhesive is preferably an adhesive containing athermoplastic polyester resin component as the main component, from thesame reason as mentioned above.

The above-mentioned bombard treatment is preferably a bombard treatmentutilizing a gas which makes polar groups be present on the surface ofthe film after the bombard treatment, from the same reason as mentionedabove.

As the substrate, a plastic sheet such as a vinyl chloride resin(including one other than a soft type), a polyester resin or apolyethylene resin, or a metal plate such as a SUS plate, a galvanizedsteel plate, a galvanium steel plate or an aluminum plate, may, forexample, be preferably used.

At present, products obtained by laminating an ETFE film on a plasticsheet such as a vinyl chloride resin, a polyester resin or apolyethylene resin, may be available. However, products which areexcellent in water resistance and moisture vapor resistance can not beavailable. This is attributable to the fact that by the surfacetreatment of the film, the above-mentioned WBL layer is formed on thefilm. According to the above-mentioned method for producing a laminateof the present invention, an ETFE film and a plastic film can be bondedwith each other by a common dry lamination method, for example, as shownin FIG. 7. According to the method for producing a laminate of thepresent invention, lamination with a treatment rate of from 5 to 40m/min can be carried out, and an adequate workability can be obtained.

It is preferred to make the films pass between nip rolls during thelamination. The linear pressure (lamination pressure by nip rolls) ispreferably from 5 to 10 kgf/cm. The laminate thus produced preferablyundergoes heat curing. However, an adequate bonding strength can beobtained with a room temperature curing at a level of 25° C. Further,the substrate to be laminated with the ETFE film by this laminationmethod, is not limited to plastic containing no fluorine represented byvinyl chloride, polyester, polypropylene or acryl, and variousfluororesins may be laminated.

Further, as a method for laminating the ETFE film with a metal, a methodfor bonding the film on a metal plate of which the surface for bondingis increased by sandblast or by etching by chemicals, by heat melting ata temperature of at least the melting point, or a method of heatlamination at a temperature of at a level of from 70 to 230° C. by usingan adhesive, is employed. The former method is a lamination methodutilizing the fact that with regard to the ETFE laminate metal plate,the melting adhesion property of ETFE to the metal is excellent, and anexcellent adhesion strength and boiling water resistance can beobtained. However, e.g. the blast apparatus or the etching apparatustends to be large scaled, such being undesirable in view of cost. On theother hand, in the latter method, strong adhesion can be obtained at thetime of lamination, by selecting a suitable adhesive. However, the WBLlayer is newly formed on the surface of the fluoro film, by the surfacetreatment for adhesion, whereby a laminate which is excellent in boilingwater resistance can not be prepared.

On the contrary, according to the above-mentioned process for producinga laminate of the present invention, by a common dry lamination method,for example, as shown in FIG. 8, the bonding of an ETFE film with ametal plate can be made possible. According to this method, laminationwith a treatment rate of from 5 to 40 m/min can be carried out and anadequate workability can be obtained. Further, a curing after thelamination is not required. It is preferred to make the films passbetween nip rolls during the lamination. When the nip rolls are used inthe above-mentioned method for producing a laminate, an ETFE film and ametal plate can be bonded with each other only by putting them betweenthe nip rolls after the adhesive is coated on the metal plate followedby drying, and such is very excellent in mass production property. Thelinear pressure is preferably from 5 to 10 kgf/cm.

Further, in the case of using a polyester type adhesive as the adhesivein the above-mentioned process for producing a laminate, the adhesiveadequately follows the extension of the ETFE film and the steel plate,during the folding process of the laminate. The substrate to belaminated with the ETFE film by this lamination method, may, forexample, be a SUS plate, a galvanized steel plate, a galvanium steelplate or aluminum.

The laminate of the ETFE film with vinyl chloride is suitable for a wallmaterial for unit bath, a wall material for coating booth or a wallpaper, etc. The laminate of the ETFE film with stainless is suitable fora top plate of gas cooking tables or a range hood fan. The laminate ofthe ETFE film with aluminum is suitable for front panel for kitchen.

EXAMPLES

Now, Examples of the present invention will be explained.

Examples 1 to 15 and Comparative Examples 1 and 2

FIG. 3 is a schematic cross-sectional view explaining an RF bombardapparatus 10 to be used for a surface treatment of an ETFE film inExamples 1 to 15 and Comparative Examples 1 and 2.

An electrode 4 and a counter electrode 5 were arranged to faced eachother in a vacuum container 1. The counter electrode 5 was grounded, andthe electrode 4 was connected with an RF power source 2 by means of amatching box 3. An atmosphere gas was supplied into the vacuum container1 from a steel gas cylinder 8 by means of a valve 7 for introducing anatmosphere gas, and the vacuum container 1 was evacuated by a vacuumpump (not shown) by means of an air outlet 6, and the predeterminedpressure was maintained. An ETFE film (tradename: AFLEX, manufactured byAsahi Glass Company Ltd., thickness: 50 μm) to be subjected to a surfacetreatment was placed either on the counter electrode (anode) 5 or on theelectrode (cathode) 4. The distance between the electrode 4 and thecounter electrode 5 was 4 cm. The atmosphere gas to be introduced intothe vacuum container 1 was any of Ar, CO₂, O₂ or N₂. The pressure in thevacuum container 1 was any of 0.67 Pa, 6.7 Pa or 67 Pa. A radiofrequency voltage of 13.56 MHz was applied between the electrode 4 andthe counter electrode 5. The RF electrical power density was 0.16 W/cm².The treating time was any of 5, 30, 100 or 300 seconds. Under conditionsas shown in Table 1, a surface-treated ETFE film was obtained in each ofExamples 1 to 15. For the Comparative Examples, an ETFE film having acorona treatment (under a condition of 200 W·min/m² in the air, the sameapplies to the following corona treatments) applied thereto (ComparativeExample 1) and a surface-untreated ETFE film (Comparative Example 2)were employed.

Then, as a dibasic acid, a dibasic acid comprising 50 mol % ofterephthalic acid, 30 mol % of isophthalic acid and 20 mol % of subericacid was prepared. As a diol, a diol comprising 30 mol % of ethyleneglycol and 70 mol % of 1,4-butanediol was prepared. The dibasic acid andthe diol were mixed with a molar ratio of about 1:1, followed byreaction at 240° C. for 10 hours, to obtain a polyester resin having anumber average molecular weight of 30000. The polyester resin had anacid value of 3. Then, to 100 g of the polyester resin obtained in theabove-mentioned reaction, 4 g of a bisphenol A type epoxy resin havingan epoxy equivalent of 700, the amount of which was required for aterminal epoxy modification, was added, followed by reaction at 180° C.for 3 hours, to obtain a polyester resin having all terminal carboxylgroups undergone an epoxy modification. The resin was dissolved inmethyl ethyl ketone, to prepare an adhesive having a solid content of50%. Hereinafter the adhesive will be referred to as adhesive A.

On the other hand, by using 50 mol % of terephthalic acid, 30 mol % ofisophthalic acid and 20 mol % of suberic acid, as dibasic acids, and 20mol % of ethylene glycol and 80 mol % of neopentyl glycol, as diols,were reacted at 240° C. for 10 hours, to obtain a polyester resin havinga number average molecular weight of 30000, and the resin was used as anadhesive B.

On each of ETFE films subjected to the surface treatment as mentionedabove in Examples 1 to 15 and Comparative Examples 1 and 2, the adhesiveA or B was coated by 50 μm applicator, followed by drying at 70° C. for2 minutes to obtain an adhesive layer having a thickness of 15 μm asdried.

Then, the ETFE film and a transparent vinyl chloride (thickness: 200 μm)were laminated under a linear pressure of 10 kgf/cm. Here, the conditionfor bonding was such that the lamination was carried out at 120° C. for1 second in the case of using the adhesive A, and at 70° C. for 1 secondin the case of using the adhesive B.

After the lamination, a post-curing was carried out at 70° C. for 10hours. Then, a T-peeling test was carried out at a peeling rate of 50mm/min, whereupon bonding strength between the ETFE film and thetransparent vinyl chloride under ordinary state (23° C.±2° C., relativehumidity 50±5%) (hereinafter referred to as bonding strength underordinary state) was measured with respect to each of Examples 1 to 15and Comparative Examples 1 and 2.

Further, after the post-curing at 70° C. for 10 hours was carried outafter the lamination, the laminate was subjected to boiling for 5 hours,and left to stand one day at room temperature. Then, a T-peeling testwas carried out at a peeling rate of 50 mm/min, whereupon the bondingstrength between the ETFE film and the transparent vinyl chloride(hereinafter referred to as bonding strength after boiling) was measuredwith respect to each of Examples 1 to 15 and Comparative Examples 1 and2.

The results are shown in Table 1. In the Table, corona means a coronatreatment, and the same applies hereinafter.

Table 1 shows results obtained when the adhesive A was employed.However, the same results were obtained when the adhesive B wasemployed.

TABLE 1 Conditions for treatment Bonding strength Distance UnderTreatment Film- between the Treatment ordinary After Type of pressureplaced electrodes time state boiling gas [Pa] electrode [mm] [sec][gf/cm] [gf/cm] Examples 1 Ar 0.67 Anode 40 30 1500 1490 2 Ar 6.7 Anode40 30 1510 1480 3 Ar 67 Anode 40 30 1490 1470 4 Ar 0.67 Cathode 40 301530 1500 5 Ar 6.7 Cathode 40 30 1550 1510 6 Ar 67 Cathode 40 30 15401510 7 Ar 6.7 Cathode 40 5 1530 1510 8 Ar 6.7 Cathode 40 100 1500 1460 9Ar 6.7 Cathode 40 300 1410 1380 10  O₂ 0.67 Cathode 40 30 1480 1490 11 O₂ 6.7 Cathode 40 30 1420 1400 12  CO₂ 0.67 Cathode 40 30 1500 1490 13 CO₂ 6.7 Cathode 40 30 1490 1490 14  N₂ 0.67 Cathode 40 30 1530 1540 15 N₂ 6.7 Cathode 40 30 1490 1460 Comp. Exs. 1 Corona — — — — 1200 700 2Untreated — — — — 50 5

As evident from Table 1, in each of Examples 1 to 15 of the presentinvention, an excellent bonding property could be obtained. Further, itis apparent that in each of Examples 1 to 15, even after boiling, anexcellent bonding property could be maintained. On the other hand, inComparative Examples 1 wherein the corona treatment was applied,particularly the bonding strength after boiling was low, and inComparative Example 2 wherein the ETFE film was untreated, both bondingstrengths under ordinary state and after boiling were low.

Examples 16 to 30 and Comparative Examples 3 and 4

On the treated surface of each of ETFE films (15 cm×8 cm) obtained bythe surface treatment in the same manner as in Examples 1 to 15, thesame size of EVA (an ethylene-vinyl acetate copolymer having a vinylacetate content of 6 wt %, having 700 ppm of a hindered amine type lightstabilizer, 500 ppm of a heat stabilizer and 3000 ppm of an ultravioletabsorber added thereto, and having a thickness of 470 μm) film waspressed by a metal press preliminarily set at 145° C., under a surfacepressure of 10 kgf/cm² for 15 minutes, for lamination. After thelamination, the temperature was cooled to room temperature, a T-peelingtest was carried out at a peeling rate of 50 mm/min, whereupon adhesivestrength between the ETFE film and the EVA film was measured. In thesame manner, adhesion strength between the ETFE film having a coronatreatment applied thereto and the EVA film (Comparative Example 3) andan adhesion rate between a surface-untreated ETFE film and the EVA film(Comparative Example 4) were measured. The results are shown in Table 2.

TABLE 2 Conditions for treatment Distance EVA Treatment Film- betweenthe Treatment adhesion Type of pressure placed electrodes time strengthgas [Pa] electrode [mm] [sec] [gf/cm] Examples 16 Ar 0.67 Anode 40 30790 17 Ar 6.7 Anode 40 30 750 18 Ar 67 Anode 40 30 740 19 Ar 0.67Cathode 40 30 810 20 Ar 6.7 Cathode 40 30 820 21 Ar 67 Cathode 40 30 80022 Ar 6.7 Cathode 40 5 810 23 Ar 6.7 Cathode 40 100 830 24 Ar 6.7Cathode 40 300 720 25 O₂ 0.67 Cathode 40 30 800 26 O₂ 6.7 Cathode 40 30790 27 CO₂ 0.67 Cathode 40 30 820 28 CO₂ 6.7 Cathode 40 30 800 29 N₂0.67 Cathode 40 30 790 30 N₂ 6.7 Cathode 40 30 760 Comp. Exs.  3 Corona— — — — 400  4 Untreated — — — — 20

As evident from Table 2, in each of Examples 16 to 30 of the presentinvention, an excellent adhesion strength could be obtained. On thecontrary, in each of Comparative Examples 3 and 4, the adhesion strengthwas low.

Examples 31 to 45

In FIG. 4 is a schematic cross-sectional view explaining a DC bombardapparatus 20 to be used for a surface treatment of an ETFE film inExamples 31 to 45.

An electrode 14 and a counter electrode 15 were arranged so that theyfaced each other, in a vacuum container 11. The counter electrode 15 wasgrounded, and the electrode 14 was connected with a DC power source 12.An atmosphere gas was supplied into the vacuum container 11 from a steelgas cylinder 18 by means of a valve 17 for introducing an atmospheregas, and the vacuum container 11 was evacuated by a vacuum pump (notshown) by means of an air outlet 16, whereby a predetermined pressurewas maintained. An ETFE film (tradename: AFLEX, manufactured by AsahiGlass Company Ltd., thickness: 50 μm) to be subjected to a surfacetreatment, was placed either on the counter electrode (anode) 15 or onthe electrode (cathode) 14. The distance between the electrode 14 andthe counter electrode 15 was 4 cm. The atmosphere gas to be introducedto the vacuum container 11 was any of Ar, CO₂, O₂ or N₂. The pressure inthe vacuum container 1 was any of 0.67 Pa, 6.7 Pa or 67 Pa. A directcurrent voltage was applied between the electrode 14 and the counterelectrode 15. The DC electric power density was 0.16 W/cm². Thetreatment time is any of 5, 30, 100 or 300 seconds. Under conditionsshown in Table 3, a surface-treated ETFE film was obtained in each ofExamples 31 to 45.

The film was bonded to a transparent vinyl chloride by using theadhesive A or B in the same manner as in Example 1, and bonding strengthunder ordinary state and bonding strength after boiling were measured.The results are shown in Table 3.

Table 3 shows results obtained when the adhesive A was employed.However, the same results were obtained when the adhesive B wasemployed.

TABLE 3 Conditions for treatment Bonding strength Distance UnderTreatment Film- between the Treatment ordinary After Type of pressureplaced electrodes time state boiling Examples gas [Pa] electrode [mm][sec] [gf/cm] [gf/cm] 31 Ar 0.67 Anode 40 30 1500 1460 32 Ar 6.7 Anode40 30 1480 1470 33 Ar 67 Anode 40 30 1500 1470 34 Ar 0.67 Cathode 40 301510 1470 35 Ar 6.7 Cathode 40 30 1500 1460 36 Ar 67 Cathode 40 30 14801460 37 Ar 6.7 Cathode 40 5 1490 1450 38 Ar 6.7 Cathode 40 100 1500 146039 Ar 6.7 Cathode 40 300 1500 1460 40 O₂ 0.67 Cathode 40 30 1500 1480 41O₂ 6.7 Cathode 40 30 1460 1430 42 CO₂ 0.67 Cathode 40 30 1470 1460 43CO₂ 6.7 Cathode 40 30 1480 1500 44 N₂ 0.67 Cathode 40 30 1510 1470 45 N₂6.7 Cathode 40 30 1450 1450

As evident from Table 3, in each of Examples 31 to 45 of the presentinvention, an excellent bonding property could be obtained. Further, itis apparent that in each of Examples 31 to 45, even after boiling, anexcellent bonding property could be maintained.

Examples 46 to 60

Each of ETFE films obtained by the surface treatment in the same manneras in Examples 31 to 45, was laminated with an EVA film in the samemanner as in Example 16, to carry out Examples 46 to 60. The adhesionstrength of a laminate film thus obtained was measured, and the resultsare shown in Table 4.

TABLE 4 Conditions for treatment Distance between Treat- EVA TreatmentFilm- the ment adhesion Type of pressure placed electrodes time strengthExamples gas [Pa] electrode [mm] [sec] [gf/cm] 46 Ar 0.67 Anode 40 30730 47 Ar 6.7 Anode 40 30 720 48 Ar 67 Anode 40 30 750 49 Ar 0.67Cathode 40 30 800 50 Ar 6.7 Cathode 40 30 780 51 Ar 67 Cathode 40 30 80052 Ar 6.7 Cathode 40 5 800 53 Ar 6.7 Cathode 40 100 780 54 Ar 6.7Cathode 40 300 750 55 O₂ 0.67 Cathode 40 30 750 56 O₂ 6.7 Cathode 40 30770 57 CO₂ 0.67 Cathode 40 30 800 58 CO₂ 6.7 Cathode 40 30 830 59 N₂0.67 Cathode 40 30 750 60 N₂ 6.7 Cathode 40 30 740

As shown in Table 4, it is apparent that in each of Examples 46 to 60 ofthe present invention, an excellent adhesion strength could be obtained.

Examples 61 to 65 and Comparative Examples 5, 6 and 7

Then, functional groups on the surface of the surface-treated ETFE filmwere studied. The functional groups on the surface were identified by anESCA method and a chemical modification method.

In the ESCA method, O_(1S) and C_(1S) peaks on the surface of thesurface-treated ETFE film were measured, and the functional groups wereidentified by the chemical shift. For the measurement of the chemicalshift, peaks were subjected to fitting by Gauss-Lorenz function toseparate into each component, and each functional group was identifiedby the chemical shift of each separated component. The correspondencebetween the chemical shift and the functional groups was carried out bycalculating the orbital energy of a unit structural molecule by amolecular orbital method (ab-initio method).

In the chemical modification method, a reagent gas containing heteroatoms which selectively react with specific functional groups wasadhered on the surface of the surface-treated ETFE film by a reaction,and the presence or absence of hetero atoms on the surface of the ETFEfilm was measured by ESCA, whereupon the presence or absence of thespecific functional groups was analyzed.

Identification of the hydroxyl groups was carried out in such a mannerthat the surface-treated ETFE film was contacted with a vapor of(CClF₂CO)₂O (chlorodifluoroacetate anhydride) for 4 hours, followed bywashing with ethanol, the surface of the washed ETFE film was analyzedby ESCA, and the presence or absence of Cl on the surface was observed.When the hydroxyl groups were present on the surface, the reaction:

—OH+(CClF₂CO)₂O→—O—COCClF₂+CClF₂COOH

would take place, and accordingly Cl would be present on the surface ofthe ETFE film even after washed with ethanol.

Identification of the carbonyl groups was carried out in such a mannerthat the surface-treated ETFE film was contacted with a vapor ofhydrazine aqueous solution (1:1) for 4 hours, the surface of the ETFEfilm was analyzed by ESCA, and the presence or absence of N on thesurface was observed. When the carbonyl groups were present on thesurface, the reaction:

RR′C═O+(H₂N)₂→RR′C═N—NH₂

wherein each of R and R′ which are independent of each other, is analkyl group or hydrogen, would take place, and accordingly N would bepresent on the surface of the ETFE film.

By carrying out the surface treatment of an ETFE film in the same manneras in Example 2, an ETFE film of the Example 61 was obtained. Thesurface of the ETFE film was measured by ESCA, and the results are shownin FIG. 5. Further, as a comparison, the surface of a corona-treatedfilm (Comparative Example 5) was measured by ESCA, and the results areshown in FIG. 6. Both were O_(1S) spectra. The peak top of each of thesepeaks was within a binding energy range of from 533 to 534 eV. Then,each peak was subjected to fitting by Gauss-Lorenz function to separateinto components A and B, and functional groups were identified from thechemical shift of respective separated components. The peak A and thepeak B were estimated to be attributable to hydroxyl groups and carbonylgroups, respectively.

Then, functional groups of each of films in Examples 62, 63, 64 and 65obtained by carrying out the surface treatment of an ETFE film in thesame manner as in Examples 2, 11, 13 and 15, respectively, andcorona-treated film (Comparative Example 6) was identified by thechemical modification method. To confirm the presence or absence ofinfluences by physical adsorption, the identification was carried outalso with respect to a surface-untreated ETFE film (Comparative Example7). The results are shown in Table 5. In Table 5, a case where heteroatoms of the reaction reagent were detected, is represented by “◯”, anda case where they were not detected, is represented by “—”.

TABLE 5 Reaction Reaction functional Ex. Ex. Ex. Ex. Comp. Comp. reagentgroup 62 63 64 65 Ex. 6 Ex. 7 (CClF₂CO)₂O Hydroxyl ◯ ◯ ◯ ◯ — — groupHydrazine Carbonyl ◯ ◯ ◯ ◯ ◯ — group

The ETFE films of Examples 62, 63, 64 and 65, and ETFE films of theComparative Examples 6 and 7, were contacted with a vapor of (CClF₂CO)₂Ofor 4 hours, followed by washing with ethanol, and the surfaces of thewashed ETFE films were analyzed by ESCA, to observe the presence orabsence of Cl on the surfaces of the films. As a result, Cl was detectedon the ETFE films of Examples 62, 63, 64 and 65, whereby it becameapparent that hydroxyl groups were present on the surfaces of the ETFEfilms of Examples 62, 63, 64 and 65. On the surfaces of the ETFE filmsof Comparative Examples 6 and 7, no detectable amount of hydroxyl groupswas present.

Further, the ETFE films of Examples 62, 63, 64 and 65 and ETFE films ofComparative Examples 6 and 7, were contacted with a vapor of a hydrazineaqueous solution (1:1) for 4 hours, and the surfaces of the ETFE filmswere analyzed by ESCA, to observe the presence or absence of N on thesurfaces. As a result, N was detected on the ETFE films of Examples 62,63, 64 and 65 and the ETFE film of Comparative Example 6, whereby itbecame apparent that carbonyl groups were present on the surfaces of theETFE films of Examples 62, 63, 64 and 65 and the ETFE film ofComparative Example 6. On the surface of the ETFE film of ComparativeExample 7, no detectable amount of carbonyl groups was present.

The ETFE film of Comparative Example 7 was not modified at all by thechemical modifications by either reagent. Accordingly, any of hydroxylgroups and carboxyl groups detected on the ETFE films of Examples 62,63, 64 and 65, and carboxyl groups detected on the ETFE film ofComparative Example 6, were not attributable to the physical adsorptionof the reagent.

The apparatus to be used for the measurement by ESCA was Model 5500manufactured by PHI. As the X-ray source, homogeneous AlKa-rays wereemployed with 14 kV at 500 W. The X-ray irradiated area was 7 mm×2 mm,the analysis area (photo-electron detection area) was 0.8 mmφ, thephoto-electron detection angle was 70°, the neutral electron rays energywas 0.1 eV, and the Pass Energy of the photo-electron was 23.5 eV.

Examples 66 to 70 and Comparative Examples 8 and 9

Then, the relation between the bonding strength and conditions ofsurface irregularities of the surface-treated ETFE film was studied.

By applying a surface treatment to ETFE films in the same manner as inExamples 1, 2, 10, 12 and 14, ETFE films of Examples 66, 67, 68, 69 and70 were obtained, respectively. Further, as a comparison, ETFE films ofan ETFE film having a corona treatment applied thereto (ComparativeExample 8) and an ETFE film having no surface treatment applied thereto(Comparative Example 9) were prepared. With respect to each of the aboveETFE films, R_(a) was measured by using AFM at non-contact movementdynamic mode, and the results are shown in Table 6.

TABLE 6 Bonding strength Bonding under strength EVA ordinary afteradhesion Surface state boiling strength roughness [gf/cm] [gf/cm][gf/cm] Ex. 66  6.7 nm 1520 1470 800 Ex. 67  9.6 nm 1460 1460 810 Ex. 68 8.4 nm 1500 1470 780 Ex. 69  9.2 nm 1470 1500 750 Ex. 70 10.0 nm 15301440 830 Comp. Ex. 8 20.3 nm 1150 650 410 Comp. Ex. 9 13.0 nm 30 5 30

R_(a) of each of ETFE films in Examples 66 to 70 of the presentinvention was smaller than the surface-untreated ETFE film (ComparativeExample 9). The surface treatment of the present invention did notroughen the surface of the films. This means that the surface treatmentmethod of the present invention is a very uniform and mild treatment.The ETFE films in Examples 66 to 70 of the present invention providedexcellent bonding strength and adhesion strength. The surfaces of theETFE films in Examples 66 to 70 were not under significantly irregularconditions (corn-like projections were not formed), and the crystallinestructure under the surface-untreated state was not impaired. Thebonding strength and the adhesion strength were measured in the samemanner as in Example 1 and Example 16, respectively.

Example 71

FIG. 7 is a schematic oblique view explaining an apparatus and a processfor producing a laminate of an ETFE film with a vinyl chloride film. Inthe production apparatus, on an ETFE film 35 supplied from an ETFE filmroll 31, an adhesive in an adhesive chamber 32 was coated by gravurerolls 33. Then, the adhesive was dried in a drying furnace 34, and theETFE film 35 having the adhesive as dried coated thereon and a vinylchloride film 38 supplied from a vinyl chloride roll 37 were made topass between nip rolls 36 for lamination, to produce a laminate 39.

The adhesive to be used in the present example was as same as theadhesive A to be used in Example 1.

Firstly, one side of an ETFE film having a thickness of 50 μm(tradename: AFLEX, manufactured by Asahi Glass Company Ltd.) Wagsubjected to an RF bombard treatment. The conditions for treatment wereas defined in the above-mentioned Example 2. On the surface subjected tothe RF bombard treatment of the ETFE film 35 thus treated, theabove-mentioned adhesive A was coated by the gravure rolls 33, followedby drying in the drying furnace 34 at 100° C., to obtain an adhesivelayer having a thickness of 5 μm as dried.

Then, the ETFE film 35 having the dried adhesive layer and the vinylchloride film 38 having a thickness of 200 μm were made to pass betweenthe nip rolls 36 maintained at 130° C. for lamination, and the laminateof Example 61 was obtained. The linear pressure of the nip rolls 36 was10 kgf/cm, and the lamination rate was 12 m/min. After being left tostand one day at room temperature, the laminate was subjected to aT-peeling test at a peeling rate of 20 mm/min, whereupon a bondingstrength of 1530 gf/cm was obtained. Further, the test specimen wasimmersed in a boiling water for 5 hours, and subjected to a T-peelingtest at a peeling rate of 20 mm/min, whereupon the bonding strength was1490 gf/cm, thus indicating no decrease in the bonding strength.

Example 72

FIG. 8 is a schematic oblique view explaining an apparatus and a processfor producing a laminate of an ETFE film with a SUS plate. In theproduction apparatus, an adhesive in an adhesive chamber 42 was coatedon a SUS plate 45 supplied from a SUS plate roll 41 by gravure rolls 43.Then, the adhesive was dried by a drying furnace 44, and the SUS plate45 having the adhesive as dried coated thereon and an ETFE film 48supplied from an ETFE film roll 47 were made to pass between nip rolls46 for lamination, to produce a laminate 49, which was finally wound toobtain a laminate roll 50.

In the present Example, fierily, one side of an ETFE film having athickness of 50 μm (tradename: AFLEX, manufactured by Asahi GlassCompany Ltd.) Wag subjected to an RF bombard treatment. The conditionsfor treatment were as defined in the above-mentioned Example 2. Then,the adhesive A prepared in Example 1 was coated on a SUS 430 plate 45which was degreased by acetone, by gravure rolls 43, followed by dryingin a drying furnace 44 at 200° C., to obtain an adhesive layer having athickness of 5 μm as dried.

Subsequently, the ETFE film 48 which was subjected to the RF bombardtreatment in the above-mentioned manner, and the SUS 430 plate 45 havingthe adhesive coated thereon, were made to pass between nip rolls 46maintained at 120° C. for lamination, to produce a laminate 49. Thelinear pressure of the nip rolls 46 was 10 kgf/cm, and the laminationrate was 12 m/min. After being left to stand one day at roomtemperature, the laminate was subjected to a 180° peeling test at apeeling rate of 20 mm/min, whereupon the bonding strength of 1500 gf/cmwas obtained. Further, the test specimen was immersed in a boiling waterfor 5 hours, and the bonding strength of 1440 gf/cm was obtained.

Examples 73 and 74

ETFE films of Examples 73 and 74 were obtained by carrying out thesurface treatment on ETFE films by the DC bombard treatment in the samemanner as in Examples 32 and 33, respectively. With respect to suchfilms, functional groups on the surface were identified by using thepeak shift of ESCA and the chemical modification method in the samemanner as in Examples 61 and 62, whereupon it became apparent thathydroxyl groups and carbonyl groups were mainly present.

Then, with respect to the ETFE films of Examples 73 and 74, the bondingstrength with a transparent vinyl chloride having a thickness of 200 μmwas measured, by using the above-mentioned adhesive A, in the samemanner as in Example 1. With the ETFE film of Example 73, a value of1520 gf/cm was obtained, and with the ETFE film of Example 74, a valueof 1490 gf/cm was obtained, each indicating a high bonding strength.

Further, by using the above-mentioned adhesive B, the bonding strengthwith a transparent vinyl chloride having a thickness of 200 μm wasmeasured in the same manner as in Example 1. With the ETFE film ofExample 73, a value of 1500 gf/cm was obtained, and with the ETFE filmof Example 74, a value of 1470 gf/cm was obtained, each indicating ahigh bonding strength.

Example 75

One side of an ETFE film (tradename: AFLEX, manufactured by Asahi GlassCompany Ltd.) having a thickness of 50 μm was subjected to a DC bombardtreatment. The conditions for treatment were as defined in theabove-mentioned Example 33. In the same manner as in Example 71,lamination with a vinyl chloride film was carried out, and a T-peelingtest was carried out, whereupon a bonding strength of 1470 gf/cm wasobtained. Further, the test specimen was immersed in a boiling water for5 hours, and subjected to a T-peeling test, whereupon a bonding strengthof 1460 gf/cm was obtained, thus indicating no decrease in bondingstrength.

Example 76

One side of an ETFE film (tradename: AFLEX, manufactured by Asahi GlassCompany Ltd.) having a thickness of 50 μm was subjected to a DC bombardtreatment. The conditions for treatment were as defined in theabove-mentioned Example 33. In the same manner as in Example 72, theETFE film was laminated on an SUS plate to produce a laminate. Afterbeing left to stand for one day at room temperature, the laminate wassubjected to a 180° peeling test at a peeling rate of 20 mm/min,whereupon a bonding strength of 1450 gf/cm was obtained. Further, thetest specimen was immersed in a boiling water for 5 hours, whereupon abonding strength of 1480 gf/cm was obtained.

Comparative Example 10

Firstly, one side of an ETFE film (tradename: AFLEX, manufactured byAsahi Glass Company Ltd.) having a thickness of 50 μm was subjected to acorona discharge treatment in the air. The above-mentioned adhesive Awas coated on the surface by gravure rolls, followed by drying at 100°C. to obtain an adhesive layer having a thickness of 5 μm was dried.Then, the ETFE film subjected to the corona discharge treatment and avinyl chloride film having a thickness of 200 μm were made to passbetween nip rolls maintained at 110° C. for lamination. The linearpressure of the nip rolls was 10 kgf/cm, and the lamination rate was 12m/min. After being left to stand for one day at room temperature, thelaminate was subjected to a T-peeling test at a peeling rate of 20mm/min, whereupon a bonding strength of 1170 gf/cm was obtained.However, after the laminate was immersed in a boiling water for 5 hours,the bonding strength was as low as 720 gf/cm.

Examples 77 to 90 and Comparative Examples 11 and 12

Now, the relation between the bonding strength and the amount offluorine transferred of the ETFE film will be shown. In Examples 77, 78,79 and 80, the surface treatment was carried out, and the bondingstrength was measured, in the same manner as in Examples 1, 2, 4 and 5,respectively. In Examples 81, 82, 83 and 84, the surface treatment wascarried out, and the bonding strength was measured, in the same manneras in 32, 33, 35 and 36, respectively. In Examples 85, 86, 87, 88, 89and 90, the surface treatment was carried out, and the bonding strengthwas measured, in the same manner as in Examples 10, 11, 12, 13, 14 and15, respectively. In Comparative Example 11, the surface treatment inthe same manner as in Comparative Example 1 was carried out, and inComparative Example 12, the surface was not treated. In ComparativeExamples 11 and 12, the bonding strength was measured in the same manneras in Comparative Examples 1 and 2, respectively. An aluminum thin platewas hot-pressed on the surface of each of ETFE films of theabove-mentioned Examples and Comparative Examples, at a heatingtemperature of 100° C. under a surface pressure of 21 kgf/cm for apressing time of 10 minutes, followed by cooling to room temperature,and the ETFE film was separated off from the aluminum thin plate,whereupon the amount of fluorine transferred on the surface (the surfacewhich was in contact with the ETFE film) of aluminum was measured. Thebonding strength and values of the amount of fluorine transferred areshown in Table 7.

TABLE 7 Conditions for Bonding strength treatment Under After Amount ofType of ordinary boiling fluorine gas Method state [gf/cm] [gf/cm]transferred Example 77 Ar RF bombard 1510 1480 0.08 Example 78 Ar RFbombard 1490 1470 0.1 Example 79 Ar RF bombard 1550 1510 0.09 Example 80Ar RF bombard 1540 1510 0.08 Example 81 Ar DC bombard 1480 1470 0.09Example 82 Ar DC bombard 1500 1470 0.12 Example 83 Ar DC bombard 15001460 0.08 Example 84 Ar DC bombard 1480 1460 0.11 Example 85 O₂ RFbombard 1470 1480 0.09 Example 86 O₂ RF bombard 1460 1470 0.11 Example87 CO₂ RF bombard 1560 1480 0.08 Example 88 CO₂ RF bombard 1500 15100.10 Example 89 N₂ RF bombard 1520 1490 0.08 Example 90 N₂ RF bombard1540 1450 0.09 Comparative Corona Example 11 treatment 1200 700 0.98Comparative Untreated 50 5 0.2 Example 12

As shown in Table 7, the amount of fluorine transferred of the ETFE filmof the present invention was extremely small, and indicates a lowervalue than the value of the film having no surface treatment appliedthereto (Comparative Example 12). Namely, the ETFE film having the RFbombard treatment or the DC bombard treatment applied thereto of thepresent invention, has a small amount of fluorine transferred to thesurface of aluminum, and has an excellent bonding strength. On thecontrary, the ETFE film having the corona discharge treatment appliedthereto (Comparative Example 11) has a large amount of fluorinetransferred, i.e. it has a large amount of fluorine transferred to thesurface of aluminum, and is poor in bonding strength. As shown here, thebonding strength of the surface-treated ETFE film shows a high valuewhen the amount of fluorine transferred is small.

INDUSTRIAL APPLICABILITY

According to the present invention, an ETFE film having an extremelyexcellent bonding strength and a laminate employing the ETFE film can beobtained.

Further, according to a process for producing a laminate of the presentinvention, a laminate of an ETFE film having an excellent bondingproperty with a plastic sheet such as vinyl chloride can be producedwith a good mass production property.

Still further, according to the process for producing a laminate of thepresent invention, a laminate of an etfe film having an excellentbonding property with a metal plate such as sus can be produced with agood mass production property.

What is claimed is:
 1. A surface-treated tetrafluoroethylene-ethylenecopolymer film, wherein polar groups are present on the surface of saidsurface-treated film, and the surface roughness R_(a) of the surface ofthe surface-treated film is at most the surface roughness R_(a) of thesurface of the same tetrafluoroethylene-ethylene copolymer film whichhas not been surface-treated and the amount of fluorine atoms present onthe surface of an aluminum plate obtained by hot-pressing the aluminumplate on the surface of said surface-treated film at 100° C. under asurface pressure of 21 kgf/cm² for 10 minutes, followed by cooling toroom temperature and separation, is at most one time of the amount offluorine atoms present on the surface of an aluminum plate obtained bysaid hot-pressing of said aluminum plate on the surface of the sametetrafluoroethylene-ethylene copolymer film which has not beensurface-treated followed by cooling to room temperature and separation.2. The surface-treated tetrafluoroethylene-ethylene copolymer filmaccording to claim 1, wherein hydroxyl groups and/or carbonyl groups arepresent as the polar groups.
 3. A laminate which comprises a substrateand the surface-treated tetrafluoroethylene-ethylene copolymer film asdefined in claim 1 laminated on a substrate so that the surface of thesurface-treated film faces said substrate.
 4. The laminate according toclaim 3, which further has an adhesive for lamination between saidsubstrate and said surface-treated tetrafluoroethylene-ethylenecopolymer film, wherein said substrate and said surface-treatedtetrafluoroethylene-ethylene copolymer film are bonded with each otherby an adhesive.
 5. The laminate according to claim 4, wherein the saidadhesive is an adhesive which contains a thermoplastic polyester resincomponent as the main component.
 6. A process for producing a laminateaccording to claim 3, which comprises laminating atetrafluoroethylene-ethylene copolymer film having an RF bombardtreatment or a DC bombard treatment applied to its surface, with anothersubstrate, by a dry lamination method.
 7. The process for producing alaminate according to claim 6, which comprises coating an adhesive forlamination on a tetrafluoroethylene-ethylene copolymer film having an RFbombard treatment or a DC bombard treatment applied to its surface,followed by drying said adhesive, and bonding another substrate and saidtetrafluoroethylene-ethylene copolymer film after said treatment withsaid adhesive for lamination by a dry lamination method.
 8. The processfor producing a laminate according to claim 7, wherein said adhesive isan adhesive which contains a thermoplastic polyester resin component asthe main component.
 9. The process for producing a laminate according toclaim 7, wherein said bombard treatment is a bombard treatment utilizinga gas which makes polar groups be present on the surface of the filmhaving the bombard treatment applied thereto.
 10. A surface-treatedtetrafluoroethylene-ethylene copolymer film according to claim 1,prepared by an RF bombard treatment or a DC bombard treatment.
 11. Asurface-treated tetrafluoroethylene-ethylene copolymer film according toclaim 10, wherein said RF bombard treatment or a DC bombard treatment isat an electric power density of from 0.01 to 0.5 W/cm².